<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <input type="text" class="tx1">
  <input type="button" value="发送验证码" id="btn1" >
  <script>
    var btn = document.getElementById("btn1");
    function fun1() {
      console.log(1);
    }
    function fun2() {
      console.log(2);
    }
    btn.addEventListener("click",fun1);
    btn.addEventListener("click",fun2);
    btn.removeEventListener("click",fun1)
  </script>
</body>
</html>